Seat belt retractor with two tensioning devices

ABSTRACT

A self-blocking belt retractor has an emergency tautening device, which is provided for the belt shaft and which can be tripped, in particular, during an accident, and has a second tautening device, which is also connected to the belt shaft and which is designed as a reversibly operating pre-tautening device. The invention is characterized in that the emergency tautening device ( 15 ) is designed to work at a higher rotating speed than the rotating speed produced by the pre-tautening device ( 11 ), and the coupling ( 13, 17, 20 ) between the pre-tautening device ( 11 ) and the belt shaft ( 14 ) is designed in such a manner that after the emergency tautening device ( 15 ) is tripped, the belt shaft ( 14 ) thereby set in a faster rotating motion brings the coupling ( 13, 17, 20 ) back into its releasing position whereby releasing the coupling connection between the belt shaft ( 14 ) and the pre-tautening device ( 11 ).

The invention relates to a self-locking belt roller with an emergency tensioning device for the belt shaft which can particularly be triggered in case of an accident and with a second pretensioning device which is also connected to the belt shaft which is in the form of a reversible-operation pretensioning device, whereby a device is provided for ending of the tensioning process effected by the pretensioning element when the emergency tensioning device is triggered.

A belt roller with the aforementioned characteristics is described in JP 2002-326558. This belt roller exhibits two tensioning devices, namely first a reverse-operation device with an electric motor as drive. This pretensioning device is intended in normal driving operations to keep the seat belt which is being worn tensioned up to occurrence of stronger accelerations or decelerations of the vehicle without occurrence of an accident, and is intended to prevent the possibility of the belt hanging loose. If an accident occurs, a further emergency tensioning device in the form of a pyrotechnically driven tensioning device is triggered, which rotates the belt shaft in the direction of winding with corresponding force and rotational speed, ensuring that there is no looseness of the belt up to active pulling of the vehicle occupants back into the seat.

With such a form of the generic type of belt roller, there is a problem of harmonisation with regard to the two belt tensioning devices, in so far as the pyrotechnic emergency tensioning device can be triggered when the electric motor pretensioning device is still functioning, and this can lead to two tensioning drives interfering with one another, so that the installed tensioning energy is not utilised to an optimum extent. In order to solve this problem, a signal-controlled cancellation of the drive connection between the electric motor and the belt shaft is already provided in JP 2002-326558.

This solution involves the disadvantage that the control technology and the coupling design are correspondingly complex. On the one hand, the point in time when the pyrotechnic emergency tensioning device must be determined and a corresponding signal has to be processed; as cancellation of the drive connection between the belt shaft and the pretensioning device enters into a tensioning process which is already running with corresponding force transfer, the coupling formed in the belt tensioner described in the generic JP patent is correspondingly complex.

The invention is therefore based on the task of excluding overlapping of the drive effect of the two tensioning devices in a self-locking belt roller with the generic characteristics in a simple fashion.

The solution of this task, including advantageous forms and further developments of the invention, results from the content of the patent claims which follow this description.

The basic concept behind the invention is that the emergency tensioning device is designed with a greater rotational speed than the rotational speed generated by pretensioning device and the coupling between the pretensioning device and belt shaft is formed in such a way that, following triggering of the emergency tensioning device, the belt shaft which by these means has been set into faster rotation takes the coupling back to its release position and therefore removes the coupling connection between belt shaft and pretensioning device. The advantage is associated with the invention, that no particular control mechanics have to be provided in order to switch off the pretensioning device, as the fast rotational acceleration of the belt shaft which necessarily occurs when the emergency tensioning device is triggered ensures the cancellation of the coupling connection between belt shaft and pretensioning device. No further measures are therefore necessary.

According to one embodiment of the invention, it is provided that the coupling between belt shaft and pretensioning device consists of a coupling bell which is connected in fixed fashion to the belt shaft and is provided with internal teeth, and of a toothed disc located on the take-off wheel of the pretensioning device and which can be controlled in order to engage in the internal teeth of the coupling bell, whereby the toothing of the coupling bell and the toothed disc are harmonised with each other in such a way that when the coupling bell is at a standstill or is turning more slowly that the drive wheel, locking takes place in the direction of winding, and when the coupling bell is rotating at a greater speed than the take-off wheel the tooth flanks of the inner teeth of the coupling bell push the toothed disc with the allocated tooth flanks out of alignment. Such a coupling connection is already known from DE 100 59 227 C1 without consideration of a particular toothing geometry. Correspondingly it is also provided for in a further development of the invention that the toothed disc is located in a slidable fashion in a recess formed in the take-off wheel between a release position lying within the contour of the take-off wheel and a locking position projecting beyond the circumference of the take-off wheel and which is held in the release position by means of a friction element.

According to embodiments of the invention, the pretensioning device can be equipped with an electric motor and the emergency tensioning device can be equipped with a pyrotechnic drive in a way which is known from the fundamental generic patent.

An embodiment of the invention is shown in the drawings, which is described in the following text. The drawings are as follows:

FIG. 1 A belt roller with two tensioning devices in a cut-out side view,

FIG. 2 The coupling connection between pretensioning device and belt shaft in an enlarged individual view in cross section, with the circumstances during pretensioning made clear,

FIG. 3 The object of FIG. 2, whereby the relationships during emergency tensioning are made clear.

The belt roller 10 shown in FIG. 1 consists in a simplified view of an arrangement of a belt shaft 14 and a pretensioning device in the form of an electric motor 11 as a drive for it; the belt roller arrangement and the electric motor 11 are connected with each other by means of a connection housing 12 which is formed as a gear housing in such a way that the drive movement of electric motor 11 can be transmitted for example by gearing not shown in detail here into rotation of a takeoff wheel 13, whereby takeoff wheel 13 is seated in the connection housing 12.

An emergency tensioning device 15, preferably pyrotechnic in nature, affects belt shaft 14; the emergency tensioning device can be in the form of a belt tensioner which is per se already known; a tensioning wheel as component of a known ball tensioning device is designated with 16, which sits on belt shaft 14 in fixed fashion. A coupling bell 17 provided with internal teeth is also connected in fixed fashion with belt shaft 14, which reaches into the take-off wheel and overlaps an inner appendage 28 of take-off wheel 13 in such a way that a coupling yet to be described can be formed. This coupling can be seen in detail in FIGS. 2 and 3.

The coupling connection between take-off wheel 13 and coupling bell 17 is shown in FIGS. 2 and 3. For this purpose, a toothed wheel 20 with outer toothing is located in a recess 19 formed in take-off wheel 13 so as to be capable of sliding. In a position, in which the toothed wheel 20 is pushed to the outside in comparison with the position shown in FIGS. 2 and 3 in such a way that the outer toothing 21 projects over the circumference of an inner appendage 28 of takeoff wheel 13, outer toothing 21 of toothed disc 20 engages with internal toothing 22 of coupling bell 17, whereby the coupling connection between take-off wheel 13 of the pretensioning device and belt 14 is created. In order to instigate the sliding movement of toothed wheel 20 towards the outside from the position shown in FIGS. 2 and 3, a friction element designated with 18 in FIG. 1 is provided, which when takeoff wheel 13 starts to rotate, first holds toothed disc 20 in fixed fashion, so that based on the relative movement which is beginning between take-off wheel 13 and friction element 18, toothed wheel 20 is pushed towards the outside along guide path 27, as described in DE 100 59 227 C1 already mentioned.

Referring to FIG. 2, the movement sequence when electric motor 11 triggers is described below, which first turns take-off wheel 13 in the direction of arrow 30, in other words in clockwise direction. As toothed disc 20 is initially held in fixed fashion in recess 19 of take-off wheel 13 due to the effect of friction element 18, a thrust movement of toothed disc 20 takes place along guide path 27 in the direction of arrow 21, so that outer toothing 21 engages with inner toothing 22 of coupling bell 17. Within this arrangement, the tooth flanks 23 of outer teeth 21 and 24 of inner teeth 22 which are orientated in the direction of rotation (Arrow 30) of take-off wheel 13 are directed approximately radially in such a way that a secure toothing engagement results. This means that the coupling bell 17 is driven in the direction of Arrow 32 (in clockwise direction), so that because of the fixed connection of coupling bell 17 with belt shaft 14, belt shaft 14 is also rotated in the direction of tensioning.

If now, during engagement of the toothing of toothed disc 20 and coupling bell 17, pyrotechnic emergency tensioning device 15 is triggered, coupling bell 17 is rotated with a correspondingly great rotational acceleration in the direction of arrow 33 (in clockwise direction), so that coupling bell 17 overtakes rotating take-off wheel 13. Tooth flanks 23 and 24 then lift up from one another, and tooth flanks 25 on outer teeth 21 and 26 on inner teeth 22 which are arranged at corresponding angles come into contact with one another, which are orientated in such a way as regards rotational direction, that toothed disc 20 with its tooth flanks 25 running on tooth flanks 26 of inner teeth 22 because of the slower rotational speed of take-off wheel 13 is pushed into recess 19 of take-off wheel 13, so that the coupling connection between take-off wheel 13 and belt shaft 14 is cancelled. As because of the “overtaking manoeuvre” of coupling bell 17 in relation to take-off wheel 13, no more forces are exercised between take-off wheel 13 and coupling bell 17, toothed disc 20 is pushed into its release position without obstacle.

The characteristics of the object of these documents which are described in the above description, the patent claims, the summary and the drawing can be of fundamental significance for the realisation of the invention in its various embodiments both individually and in any desired combinations with each other. 

1. Self-locking belt roller with an emergency tensioning device for the belt shaft which can particularly be triggered in case of an accident and with a second tensioning device designed in the form of a reversibly- operating preliminary tensioning device which is also connected to the belt shaft, whereby a device is provided for ending the tensioning process effected by the pretensioning device when the emergency tensioning device is triggered, characterised in that the emergency tensioning device (15) is designed with a greater rotational speed than the rotational speed created by the preliminary tensioning device (11), and the coupling (13, 17, 20) is formed between preliminary tensioning device (11) and belt shaft (14) in such a way, that following triggering of emergency tensioning device (15), the belt shaft (14) which is thereby caused to rotate more rapidly leads coupling (13, 17, 20) back to its release position and therefore cancels the coupling connection between belt shaft (14) and preliminary tensioning device (11).
 2. Belt roller according to claim 1, characterised in that the coupling between belt shaft (14) and preliminary tensioning device (11) consists of a coupling bell (17) connected in fixed fashion with belt shaft (14) and supplied with inner teeth, and of toothed disc (20) located on the take-off wheel (13) of preliminary tensioning device (11) which is capable of being triggered so as to engage in the inner teeth (22) of coupling bell (17), whereby toothing (23, 24, 25, 26) of coupling bell (17) and toothed disc (20) are harmonised with each other in such a way that if the coupling bell (17) is at a standstill or is rotating more slowly that coupling bell (17) turning take-off wheel (13), blocking occurs in the winding direction and if the coupling bell (17) rotates at a higher speed than the take-off wheel (13), tooth flanks (26) of inner toothing (22) of coupling bell (17) push the toothed disc (20) out of engagement with the allocated tooth flanks (25).
 3. Belt roller according to claim 2, characterised in that the toothed disc (20) is arranged in a slidable manner in a recess (19) formed in the take-off wheel (13) between a release position inside the contour of take-off wheel (13) and a blocking position projecting over the circumference of the take-off wheel (13) and which is held in the release position by a friction element (18).
 4. Belt roller according to any of claims 1 to 3, characterised in that the pretensioning device exhibits an electric motor (11) working in reverse as a drive.
 5. Belt roller according to any of claims 1 to 4, characterised in that the emergency tensioning device (15) is provided with a pyrotechnic drive. 